Extra vertices created when extruding and scaling?
You have multiple vertices on the same position. Selecting and moving on of them, reveals the other.


Make sure you are in Wireframe View mode. Toggle with Z.
Select the vertices which overlap each other. This can be done by pressing B an dragging a box select over them or by toggling the select all A which will (de)select all.
Do the remove doubles operation. Open up the specials menu in edit mode W and choose remove doubles R. This operation merges overlaying vertices together.